Davis traveled to Haiti at the request of Dr. Nathan S. Kline, who theorized that a drug was responsible for Narcisse's experiences as a zombie. Since such a drug could have medical uses, particularly in the field of anesthesiology, Kline hoped to gather samples, analyze them and determine how they worked.
Davis learned that Haitians who believed in zombies believed that a bokor's sorcery -- not a poison or a drug -- created them. According to local lore, a bokor captures a victim's ti bon ange, or the part of the soul directly connected to an individual, to create a zombie. But during his research, Davis discovered that the bokor used complex powders, made from dried and ground plants and animals, in their rituals.
Davis collected eight samples of this zombie powder in four regions of Haiti. Their ingredients were not identical, but seven of the eight samples had four ingredients in common:
In addition, the powders contained other plant and animal ingredients, like lizards and spiders, which would be likely to irritate the skin. Some even included ground glass.
The use of puffer fish intrigued Davis. Tetrodotoxin causes paralysis and death, and victims of tetrodotoxin poisoning often remain conscious until just before death. The paralysis prevents them from reacting to stimuli -- much like what Clairvius Narcisse described about his own death. Doctors have also documented cases in which people ingested tetrodotoxin and appeared dead but eventually made a complete recovery.
Davis theorized that the powder, applied topically, created irritation and breaks in the victim's skin. The tetrodotoxin could then pass into the bloodstream, paralyzing the victim and causing him to appear dead. The family would bury the victim, and the bokor would remove the body from the grave. If all had gone well, the poison would wear off and the victim would believe himself to be a zombie.
While Davis's theory is promising, it does have some holes. Next, we'll look at the controversy surrounding Davis's research.